The temperature dependence of the emf of a standard electrochemical cell is given by
`E=1.02-4.0xx10^(-5) (T-20)-9.0xx10^(-7) (T-20)^(2)`
where, T is in `.^(@)C` and E is in volts. The temperature coefficient of the emf at `30^(@)C` is :

Answer

A

Explanation

`(dE)/(dT)=d/(dT) [1.02-4xx10^(-5) (T-20)-9.0xx10^(-7) (T-20)^(2)]`
`=-0.4xx10^(-5)-9xx10^(-7)xx2T`
`=-0.4xx10^(-5) -9xx10^(-7)xx2xx30 ( :' T=30^(@)C)`
`=-5.8xx10^(-5)`